The coupling of shear walls by thin slabs in concrete high-rise buildings subjected to lateral loads is studied. The effectiveness of slab coupling is investigated using simple 2D and 3D finite element models based on a scaled experimental building. The models are validated and show the effectiveness of slab coupling, in contradiction with Eurocode 8 guidelines. A parametric study is also carried out on coupling slabs to assess their behavior and effective width. Recommendations based on parametric results are proposed to engineers for modeling slab coupled shear walls systems. Coupling induced by slabs is a complexity that must be taken into account by engineers, as it has a major impact on the behavior of a building.